Evaporator



April 1, 1941. O J, KUENHQLD 2,236,538

EVAPORATOR Filed Oct. 6, 1938 3 Sheets-Sheet 1 INVENTOR.

bffo Iffuczz/zold ATTORNE 6 April 1, 1941.

o. J. KUENHOLD 2,236,538

EVAPORATOR Filed Oct. 6, 1938 3 Sheets-Sheet 2 IN VENT OR.

BY 051,26 Yiuenho/d ATTORNEYS.

April 1, 1941.

O. J. KUENHOLD EVAPORATOR Filed Oct. 6, 1938 3 Sheets-Sheet 5 Q kw INVENTOR. B 0170 fffzmn/zaZd M zi i ys Patented Apr. 1, 1941 EVAPORATOR} I Otto J. Kuenhold, Shaker Heights, Ohio, assignor to Monmouth Products Company, Cleveland, Ohio, a corporation of Ohio Application October 6, 1938, Serial No. 233,631

6 Claims.

The present invention relates to an evaporating device particularly adapted for use in the heating, ventilating and air conditioning art, and is of the type wherein evaporation of water and its entrainment in a passing air stream is obtained by means of porous, ceramic plates disposed in a substantially vertical position in a water reservoir. The subject matter of the present application constitutes an improvement in my United States Letters Patent No. 2,166,414, granted July 18, 1939 for Humidifying system. The general object and nature of my present invention is to provide an evaporator of the type indicated having a much greater evaporation rate capacity and increased life or period of service. Additional objects and advantages of the invention shall become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims.

The annexed drawings and the following description set forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of various mechanical forms in which the principle of the invention may be used.

In said annexed drawings- Fig. 1 is a view illustrating an evaporating plate and water pan as heretofore disclosed in my aforesaid patent and upon which the present application constitutes an improvement; Fig. 2 is a sectional view taken upon a plane normal to that of Fig. 1; Fig. 3 is a partially diagrammatic figure of an evaporator plate and water pan and is for the purpose of aiding in the explanation of the principle of my invention; Fig. 4 is a top plan view of one-half of one of the evaporating plates having the improved construction; Fig. 5 is a longitudinal sectional view of the Water pan and supporting rack with one of the evaporating plates shown in position; Fig. 6 is a top plan view of the evaporator embodying the principle of my invention; Fig. 7 is a side elevational view thereof; Fig. 8 is a cross-sectional view taken substantially along line 88 of Fig. 7; Fig. 9 is an end elevational view of the cover plate and water feed apparatus for the evaporator; Fig. 10 is a right hand end elevation of the water pan; Fig. h

11 is a cross-sectional view taken substantially along line H-|l of Fig. '7; Fig. 12 is a longitudinal sectional view showing one means of varying the height of the evaporating plates with respect tothe water level; and Fig. 13 is a longitudinal sectional viewshowing an alternative means of varying the height of the evaporating plates with respect to the water level.

Now referring to Figs. 1 and 2, it will be seen that the porous, ceramic evaporating plate I shown therein is in the form of a rectangle with my aforesaid patent.

a central downwardly extending tongue 2 con tacting with the water in the water pan or reservoir 3. Projections 4 are provided in the bottom of the pan for engaging with the tongue 2 and notches 5 are provided in the upper edges of the pan 3 for engaging with the body portion of the plate I. l The above illustrated and described construction is further set forth and claimed in I have discovered, however, that by means of the presently embodied improvements in the form, contour and dimensions of the evaporating plate, that the evaporation rate or capacity can be many times increased. For example, the original plate, in the form as shown in Figs. 1 and 2 required 70 minutes after a dry plate was inserted in the water pan 3 for the entire plate to become wet, while in the presently improved construction, the plate becomes wet in 2 minutes, although the size of the new plate was relatively twice that of the old one.

These porous, ceramic evaporating plates operate generally upon the principle of absorbing water from the water pan by capillary action, thus presenting exposed wet or moistened surfaces for contact with a passing air stream.

Now referring to Fig. 3, there is shown therein an evaporating plate consisting generallyof the two half portions A and B. A series of dotted line curves a to h inclusive represent the upper limitsof the wet or moistened area of the plate at the following time intervals after the dry plate has been inserted in the water pan with the level maintained at the line marked W. L., viz.:

Time in- M indies These curves a. to 72. inclusive represent a careful copy of pencil lines made on the face of the to the 2 min. interval was selected for the outline of the ideal form of plate shown at A. For practical considerations and for commercial form, the form B has been found suitable. In this latter form of evaporating plate, the top edge i9 is horizontal with the curved corner ll merging into the straight, vertical edge l2, thence to the curved corner i3 and the bottom, straight edge It. The downwardly extending tongue l5 has an inverted V-shaped recess ll for fitting into the slots of the supporting rack 2|. A straight edge portion I8 extends across the mouth of the inverted V-shaped recess I! at a distance slightly inwardly removed therefrom and presents an abutting edge adapted to bear against the bottom of the slots of the rack 2|. The latter is laid upon the bottom of the water pan 2% and is also of inverted V-shaped crosssection with the upwardly extending marginal edges 22 which also contact with the bottom edges of the tongue portion 55 of the evaporating plate B. Transverse slots 23 are provided at intervals in the rack ii for spacing the plates 13.

I have made the discovery that if the plate is of tapered cross section, thicker at the bottom than at the top, as indicated in the transverse section of the plate in Fig. 5, the rapidity of capillary advance of Water in the plate is considerably increased. I have further discovered that if the plate is progressively thinner from the water surface upward and outward so that the curves a to it inclusive would represent contour lines of progressively reduced thickness toward the outermost edges at top and sides, as indicated by top view Fig. 4, the capillary advance of the water laterally would be more rapid and the curves a to h inclusive would extend out further laterally. This means that the plate can be extended laterally substantially as shown at l2, l3 and M, and still remain as wet in service at the extreme lateral edges as it does in the rectangular form of Figs. 1 and 2. In other words, more evaporation could be secured per plate without danger of the outer edges remainin insufiicientl'y moist for efilcient evaporating service and durability. The tapering of the plate as described not only adds to the efiicien't evaporation per plate but extends its period of efficient service as will be more fully explained later.

All city supplied water contains dissolved mineral salts and floating matter such as algae and iron oxides (rust). All city supplied water passes through iron pipes and the rust so formed by action of the water and its contents upon the inner walls of the iron mains and pipes. The floating matter in the water enters and clogs the inlet pores of the plates.

Any mineral salts dissolved in the water freely enters the inlet pores and is carried by the capillary flow outward toward the outer edges of the plates. The water itself is evaporated from the surfaces of the plates but the soluble salts accumulate on the outer edges of the plates. As the rapid Water evaporation from the surfaces of the plates reduces their temperature, the mineral accumulations on the outer edges of the plates remains soft, porous, moist and easily brushed off from time to time-each year or two normally.

Besides the mineral salts which remain permanently soluble as above described, city supplied water also contains calcium and magnesium carbonates which remain dissolved in the water if the water also contains carbon dioxide, as is almost invariably the case. But an action takes place which seems to be as follows: When the water enters the pan where it is warmed some- What by the warm air circulating around and past the pan and plates, the carbon dioxide begins to escape and continues to do so after the water enters the plates. The calcium and magnesium carbonates can then no longer be held in solution by the water, consequently they are deposited in the plates, especially near the inlet end, gradually accumulating and cutting down the pore area until water can no longer pass through the inner pores of the plates as fast as the plates can evaporate it.

A third type of clogging action occurs but this occurs either in plates not having correct outline or when plates considerably clogged by calcium and magnesium carbonates as described in the preceding paragraph are continued in service. In either one of these two cases, the outermost areas 01 the plates, last to receive the water, become dry. Evaporation then occurs within the plate generally along a sharply outlined curve, as for instance curve of Fig. l, and mineral salts are deposited along this line blocking flow of water past this line within the plate.

To prevent the first named type of clogging, that is clogging of the inlet pores of the plate by floating matter in the supplied water, I have found'it practically imperative to provide a Water filter containing a filter medium composed of the same porous material as the plates. Such a filter medium can be conveniently installed in either of the feed lines 36 or 3?. This filterin medium thus passes floating matter that will not clog the inlet pores of the plates but stops floating matter that would clog the inlet pores of the plates. The filter is then cleaned from time to time which is very much easier to do than to remove and clean all the plates.

There will then still remain in the water floating oxides formed by action of the water upon the inner wall of the metal tubing from the filter to the water pan. This too would clog the inlet pores of the plates within possibly a couple of months but to extend this time limit to a full season or two, I provide much greater inlet area such as indicated at [5, than is actually necessary. In this way I am able to extend the active efiicient service period of the inlet surface up to atime when internal plate clogging makes attention to this phase necessary.

The internal plate clogging due to calcium and magnesium carbonate deposits is provided against as follows: The uptake area is increased by the widening of the pan and plate as described in the preceding paragraph and also by the tapering of the plate, making it thicker toward the inlet area, as has been described, this tapering adds considerable to the active service period of the plate before internal clogging accumulates to the point where evaporation is impaired. The more rapid and therefore more effective capillary flow induced by the tapering formation also helps to extend the active life of the plate for other but not yet known reasons.

In addition to the steps taken as above described two other steps are taken to cope with internal deposits. I have found that certain sol- -vents and acids such as hydrochloric acid readily converts calcium and magnesium carbonates to highly soluble salts such as chlorides which can then be washed out with water substantially as if the deposits were sugar. I therefore make the plates or 'a material which is impervious to hycarbonate solvents.

drochloric acid and other calcium or magnesium In addition I make the plates of a material having rather coarse capillarity to facilitate the washing out process and at the same time provide ample voids for accumulation of internal deposits so that longest possible active service period is attained.

I have furthermore discovered that if, while the plates are in service, a solvent such as acetic acid or hydrochloric acid in relatively small and harmless quantity is added to the water in the pan from time to time, it converts insoluble accumulations in the plates to soluble salts and the capillary flow within the plates thereupon carries the said accumulations, then in soluble form, to the surface and toward the outer edges of the plates.

Figs. 6 and 11 illustrate the evaporator as assembled in a heating furnace bonnet or plenum chamber. The guides 25 on the sides of the pan 20 engage with the support rods 26 which extend through to the outer wall 21 of the furnace. A hook bolt 28 connects the inner or right hand end of the pan 20 to the ceiling or top wall 29 of the furnace and is attached by means of the nut 30. As shown in Fig. 10, an extension strip 28 may be used in the event that the hook bolt 28 is not of sufficient length. Openings 3| and 32 are provided in the inner and outer furnace walls 21 and 21' respectively for access to the evaporator pan 20 and plates B. A cover plate 33 extends over the outside wall opening 3|. A feed pipe 34 leads into the left hand or front end of the pan 20 from the feed cup 35. The water supply, if previously controlled, as from a remote control source such as a water feed regu lator located in the space to be heated, may be led into the feed cup 35 through the line 36; on the other hand, if the water feed is to be by way of a direct control instrument such as indicated at 38, the water feed line may be located as indicated at 31. A water level equalizer cup 38 has an air tube 40 which passes through the cover plate 33 and connects the cup 39 with the air pressure in the interior of the furnace. The overflow pipe 4| leads to a drain from the equalizer cup 39.

Referring now to Figs. 12 and. 13, my invention also includes means for rapidly increasing the rate of evaporation in proportion to the rate of introduction of water to the pan 20. In Fig. 12, the right hand end of the pan 20 is elevated by means of shortening the support rod 28. In Fig. 13, the supporting rack 2| is elevated by means of the lug 42 placed between the bottom of the rack 2| and the bottom of the pan 2|] in the right hand end. The range of the highest and lowest water levels are indicated in legends in Figs. 12 and 13. It has been found that where rapidly increased rates of evaporation are desired that a mere change in water level is not sufficient to meet the conditions of demand and operation. By means of varying the distance of the bottoms of the plates B with respect to the water level range; or in other words, by varying the depth of immersion of the plates, a greatly increased evaporating rate is obtainable in proportion to the rate of water supply or rate of elevation of the water level. This result is explainable by the fact that there is a substantial difference in the rate of evaporation by an individual plate between depth of immersion corresponding to a substantial amount of water immersion of the bottom of the plate and to a mere minimum wetting of the bond of the plate respectivelywIn other words, when the water level substantially coincides with the bottom of the plate, the evaporating rate of the latter is greatly reduced as compared to its evaporating rate when the water level is higher. As shown in the accompanying drawings, the bottom-of the highest plate substantially coincides with the lowest water level, so that such highest plate will at all times receive some wetting action and will thereby not become completely dry. I have found that this relative positioning of the height of the highest plate with respect to the lowest water level is of advantage, since when the plates are permitted to become alternately wet and dry, there exists a tendency for the creation of increased lime deposits in the plates. The tilting of the pan such as shown in Fig. 12, or the tilting of the plate supporting rack such as shown in Fig. 13 illustrate two methods of achieving the foregoing results and advantages.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In an evaporator, the combination of a water reservoir, a plurality of porousevaporator plates adapted to extend upwardly and outwardly from said reservoir, a supporting rack for said plates comprising an elongated strip of inverted V-shaped cross-section and having a series of spaced, vertical transverse slots for the reception of the bottom ends of said plates, and complementary recesses in said plates adapted to receive the edges of said strip adjacent said slots.

2. In an evaporator, the combination of a water reservoir, a plurality of evaporator plates composed of acid resistant ceramic porous material disposed substantially vertically in said reservoir, means for feeding water to said reservoir, and means for maintaining such water level between predetermined maximum and minimum limits, and means for locating the bottom terminal edges of said plates at varying distances with respect to said maximum and minimum water level limits.

3. In an evaporator, the combination of a water reservoir, a plurality of evaporator plates composed of acid resistant ceramic porous material disposed substantially vertically in said reservoir, means for feeding Water to said reservoir, and means for tilting said reservoir in a direction normal to the surface of said plates whereby the bottom terminal edges thereof are located at progressively varying distances with respect to the water level range in said reservoir.

4. In an evaporator, the combination of a horizontally disposed water reservoir, a supporting rack adapted to be contained in said reservoir, a plurality of evaporator plates mounted transversely in said supporting rack and with their bottom edges located in alignment with respect to said rack, and means for tilting said supporting rack with respect to said reservoir whereby the bottom edges of saidplates are located at varying distances with respect to the water level in said reservoir.

5. In an evaporator, the combination of a water reservoir, a plurality of porous evaporator plates adapted to extend upwardly and outwardly from said reservoir, and a supporting rack for said plates comprising an elongated member having a series of spaced, vertical transverse slots for the reception of the bottom ends of said plates and flanges extending from said member for supportingsaid plates by their bottom edges.

6. In an evaporator, the combination of a water reservoir, a plurality of spaced evaporator plates disposed substantially vertically in said reservoir, means for feeding water to said reservoir, means for maintaining the water level between predetermined maximum and minimum limits, and means for locating the bottom terminal edges of said plates at varying distances with respect to said maximum and minimum water levels.

OTTO J. KUENHOLD. 

